Essentially you cast 4 Arcane Blasts to stack the debuff, stand in the middle of the pack and cast 4 Arcane Explosions.
Refresh your debuff by casting one Arcane Blast on some target (preferably the one with the highest health so you don't waste time casting if the mob dies) and then keep on spamming AE.

You shouldn't however AoE as Arcane when there's only a few targets up. I'd advice you to stay on single target rotation when there's < 6 mobs.

Arcane really isn't the best spec for AoE. I have had great success with Fire by have Living Bomb on three targets (when possible) and spreading Ignite with Impact; I use Blastwave and Flamestrike when BW is on cool-down to proc Impact. Ideally, you will also want to spread Combustion, which will cause your DPS will skyrocket.

or option 4 which would be the right choice,
4 AB 3 AE than 1 AB every 3 AE to keep the buff up

^ yup for Arcane.

However, as arcane, if for whatever reason you can't get into close range to use Arcane Explosion, you can still use the old standby of cast Flamestrike->cast Blizzard and repeat. (not as good as AE but surprisingly still decent)

It all depends upon how many targets you are attempting to hit, the type of monsters, the hp of those targets, the dps of your group, the squishiness of your tank, and the shittiness of your healer.

Sometimes, burning down one priority mob with arcane blast is the correct choice, sometimes just spamming arcane explosion is.

Despite what the previous posters say, you should almost never attempt a 4 stack of arcane blast before using arcane explosion. In 5 mans, monsters simply die too quickly for this to be an effective use of your time. Pom blast one as you're running up to them if blink is on cd, but that's about it.

Fire is simply better for AoE damage.
Arcane can still do AoE damage tho, they are maybe not as good as real AE classes, but still viable.
However, the singletarget that you can do in Arcane when you can stand still, is much better than that AoE you provide.
So only if the AE is really needed for some reason, and you aren't Fire for whatever reason, you should help out AoEing.
Otherwise just stick to single-target.

Fire mages can aoe effectively with far less mana than an arcane mage can. If you plan ahead, get dots up before your mana drains, pop a gem for DB, BW, and maybe FS, you have enough left over for Combustion + Impact.

More than 3 targets, that have more than 500k hp, stack 4x ab and arcane explosion refreshing stacks everytime they are abt to fall off, other than that.. dont bother with aoe and single target to victory